US4677849A - Hydrocarbon well test method - Google Patents

Hydrocarbon well test method Download PDF

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Publication number
US4677849A
US4677849A US06/767,216 US76721685A US4677849A US 4677849 A US4677849 A US 4677849A US 76721685 A US76721685 A US 76721685A US 4677849 A US4677849 A US 4677849A
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curve
pressure
well
fluid
experimental
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Joseph Ayoub
Dominique Bourdet
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Schlumberger Technology Corp
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Schlumberger Technology Corp
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
    • E21B49/008—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells by injection test; by analysing pressure variations in an injection or production test, e.g. for estimating the skin factor

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  • This invention relates to the testing of hydrocarbon wells making it possible to determine the physical characteristics of the system consisting of a well and of a subsurface formation (also called reservoir) producing a fluid, hydrocarbons for example, through the well.
  • the invention relates to a method whereby the flow of fluid produced by the well is modified by closing or opening a valve located on the surface or in the well.
  • the resulting pressure variations are measured or recorded down-hole or on the surface as a function of the time elapsing since the beginning of the tests, i.e. since the flow modification.
  • the characteristics of the well-subsurface formation system can be deduced from these experimental data. They are analyzed by comparing the response of the subsurface formation to a change in the flow of fluid produced, with the behavior of theoretical models having well-defined characteristics and subjected to the same flow change as the investigated formation.
  • the pressure variations as a function of time characterize the behavior of the well-formation system, and the removal of fluids at constant flow, by opening an initially closed valve in the well, is the test condition which is applied to the formation and to the theoretical model.
  • the investigated system and theoretical model are identical from the quantitative as well as the qualitative viewpoints. In other words, these reservoirs are assumed to have the same physical characteristics.
  • the characteristics obtained from this comparison depend on the theoretical model: the more complicated the model, the greater the number of characteristics which can be determined.
  • the basic model is represented by a homogeneous formation with impermeable upper and lower limits and with an infinite radial extension. The flow in the formation is then radial, directed toward the well.
  • the theoretical model most currently used is more complicated. It comprises the characteristics of the basic model to which are added internal conditions such as the skin effect and the wellbore storage effect.
  • the skin effect is defined by a coefficient S which characterizes the damage or the stimulation of the part of the formation adjacent to the well.
  • the wellbore storage effect is characterized by a coefficient C which results from the difference in the flow of fluid produced by the well between the subsurface formation and the wellhead when a valve located at the wellhead is either closed or opened.
  • the coefficient C is usually expressed in barrels per psi, a barrel being equal to 0.16 m 3 and a psi to 0.069 bar.
  • each curve is characterized by one or more dimensionless numbers, each representing a characteristic (or a combination of characteristics) of the theoretical system formed by a well and a reservoir.
  • a dimensionless parameter is defined by the real parameter (pressure for example) multiplied by an expression which includes certain characteristics of the well-reservoir system so as to make the dimensionless parameter independent of these characteristics.
  • the coefficient S characterizes only the skin effect but is independent of the other characteristics of the reservoir and of the experimental conditions such as flow rate, viscosity of fluid, permeability of formation, etc.
  • the experimental curve and one of the type curves represented with the same scales of coordinates have the same form but are offset in relation to each other.
  • the offsets along the two axes, on the ordinate for pressure and on the abscissa for time, are proportional to values of characteristics of the well-reservoir system which can thus be determined.
  • Qualitative information on the subsurface formation is obtained by identifying the different flows on the network in logarithmic scale representing the experimental data. Knowing that a particular characteristic of the well-reservoir system, a vertical fracture for example, is characterized by particular flow conditions, all the different flows appearing in the graph of the experimental data are identified to select the appropriate well-reservoir system model. The characteristics of the formation are obtained by selecting a typical curve having the same form as the experimental curve and determining the offset of the axes of the coordinates of the experimental curve in relation to the theoretical curve.
  • Green's functions provide the pressure variations with respect to time created by a source (or a well--in the fluid mechanics sense) of instantaneous action and unit intensity (Dirac pulse, i.e.
  • Green's functions correspond to the derivatives with respect to time of the type curves P D used as a theoretical model. The result is that if a formation is subjected to an instantaneous action of unit intensity, the curve of subsequent pressure variations may be matched with a suitable curve P' D .
  • a well test method for determining the physical characteristics of a system consisting of a well and a subsurface formation containing a fluid and communicating with said well, this formation, homogeneous or heterogeneous, exhibiting the skin effect and/or the wellbore storage effect.
  • This method involves a change in the flow rate of the fluid and the measurement of a characteristic parameter of the pressure P of the fluid at successive time intervals ⁇ t.
  • said change of flow is produced in a short period so as to obtain a flow pulse resembling a Dirac pulse, the amplitude of this pulse being sufficiently high to enable the measurement of said parameter characteristic of the pressure P of the fluid at said successive time intervals ⁇ t.
  • the change in flow rate consists of a short period during which the well is producing, injected or closed.
  • the variations in the down-hole pressure P of the fluid are measured during said short period and then during the subsequent period of return tp the initial state of the well-formation system, and one compares the experimental pressure curve thus obtained with the curves of a double network of type curves representing, as a function of a common parameter, the pressure P and its derivative P' with respect to time, by matching the branch of the experimental curve corresponding to the short period with one of the type curves P and the branch of this curve corresponding to the subsequent period with the type curve P' of the same parameter.
  • the experimental results obtained by the method according to the invention are advantageously analyzed by matching the pressure curve measured experimentally with a network of type curves.
  • This analysis is distinguished from prior-art methods by the fact that this matching takes place with pressure P type curves only for part of the experimental curve, and for the other part of the experimental curve with derivative pressure P' type curves.
  • this analysis is performed without requiring the derivation of experimental data.
  • the type curves of the double network are plotted in logarithmic coordinates as a function of t D /C D , t D representing the dimensionless time and C D the dimensionless coefficient of the wellbore storage effect, the parameter being the quantity C D e 2S , where S is a skin effect coefficient, and this double network comprises:
  • the amplitude of the vertical and horizontal shifts necessary for the matching as well as the value determined for the parameter then making it possible to calculate the characteristics of the well-formation system, based upon the measured value of the total amount of fluid produced or injected during the short period or, for a well producing (or receiving) a fluid and whose production (or injection) is stopped for a short instant, based upon the amount of fluid which would have been produced or injected if this stopping of production or injection had not taken place.
  • the experimental curve is first translated vertically so that its second branch corresponding to the subsequent period is matched with a type curve P' D (t D /C D ), then horizontally to match its first branch with the corresponding curve P D .
  • the method according to the invention offers new means of testing hydrocarbon wells. It has general application possibilities.
  • the method can be used for example to test hydrocarbon wells in production, during short periods compared with prior-art methods.
  • Well production is interrupted only for a short instant, a few seconds, whereas in conventional methods the well closure time varies on the average from 10 hours to a few days. The result is that, by applying the present invention, the financial loss due to the interruption of production is negligible.
  • the method is also particularly well suited to the testing of new wells when the experimentation time must be short (from 1 to 20 hours) or when a flow-out onto the surface is not possible or should be avoided. This method makes it possible to obtain quickly the same information provided by conventional tests. It can be used for conducting fast tests on superposed layers of a subsurface formation and thereby obtain the vertical profile of the permeability of the formation.
  • FIG. 1 represents a network of kncwn type curves serving as a theoretical model
  • FIG. 2 represents an experimental pressure curve obtained on a well-subsurface formation system in accordance with the method of the invention, the well being previously at rest;
  • FIG. 3 represents an experimental pressure curve obtained on a well-subsurface system according to the method of the invention, the well previously producing a fluid
  • FIGS. 4 and 5 illustrate the embodiment of part of the method according to the invention, respectively in the case of a homogeneous formation and a heterogeneous formation.
  • the subsurface formation is subjected to a flow pulse and the resulting pressure variations are recorded.
  • This flow pulse can be created either by putting into production (or injecting) a well previously at rest, or by interrupting the production or injection of a well.
  • the flow pulse must be sufficiently short so as to approach ideally a Dirac pulse. It is however seen that, in practice, this flow pulse must have a sufficient amplitude so that the resulting pressure variations are measurable by means of pressure sondes currently used in the petroleum industry.
  • This method makes advantageous use of the fact that this type of disturbance (flow pulse) generates pressure variations which are compared directly with the P' D type curves already mentioned, without having to carry out the derivative of the experimental data.
  • the analysis of experimental data obtained by the method of the invention involves known networks of type curves, for example those shown in FIG. 1 (see FIG. 7 in the above-mentioned article of World Oil, or FIG. 5 of the French patent filing No. 83/07 075).
  • This is a double network. It includes a first network of curves (broken-line plot) representing the variations in the dimensionless pressure P D of the fluid as a function of the ratio t D /C D in which t D is the dimensionless time and C D is a dimensionless coefficient relating to the wellbore storage effect.
  • the second network of curves represents the product of t D /C D multiplied by the derivative P' D of the pressure P D in relation to t D /C D .
  • the curves of these two networks depend on a common parameter C D e 2S combining two physical characteristics of the well-reservoir system, namely C D defined above, and S which is a coefficient relative to the skin effect in the well. They are plotted in logarithmic coordinates, the dimensionless quantity t D C D being plotted on the abscissa.
  • k the permeability of the subsurface formation
  • h is the thickness of the formation
  • ⁇ P is the measured pressure variation
  • B is the formation volume factor relating to fluid expansion between the reservoir and surface
  • ⁇ is the viscosity of the fluid.
  • the network of FIG. 1 characterizes the behavior of a model of a homogeneous reservoir and a well exhibiting the skin effect and the wellbore storage effect.
  • the tested well is put into production or injected for a time t p as short as possible.
  • this time must, firstly, be sufficiently short so that the test principle based upon the Dirac pulse is applicable and, secondly, long enough so that the amount of fluid injected or produced is sufficient to produce a measurable pressure variation. In general, this time is of the order of few minutes and rarely exceeds 10 minutes.
  • the down-hole pressure of the fluid is measured during this production phase and then after the flow of the well is stopped.
  • a curve (FIG. 2) representing the values of the pressure P measured as a function of time ⁇ t is plotted.
  • the pressure variations ⁇ P are calculated with respect to the initial value Po.
  • the injection of fluid into the formation or the production of fluid by the formation is interrupted for a short period of time making it possible to approximate the Dirac pulse. It is this latter case which is illustrated in FIG. 3 corresponding to a well which has been in production for several hundred hours. After 500 hours, the well is closed for a period t p of about 3 minutes and then opened again. During the closure of the well, the pressure rises suddenly from M to N. Upon reopening the well, the pressure P drops from N to a value which tends toward the pressure P o which would have prevailed in the well had it not been closed. This pressure P o can easily be obtained by extrapolating the pressure P just before the well is closed. The variations ⁇ P to be taken into account are obtained by taking the difference between the pressures P and P o at different time intervals ⁇ t. The time intervals are counted from the instant t o the well is closed.
  • FIG. 4 One then plots (FIG. 4) an experimental curve (referenced ⁇ P and shown by circle-points) representing the pressure variations ⁇ P as a function of the time intervals ⁇ t in logarithmic scale. This is valid for the two embodiments described earlier (FIGS. 2 and 3).
  • the curve ⁇ P is subjected to the following transformation:
  • FIG. 4 shows that the test conducted on the well can end only two hours (approximately) after it starts, which demonstrates that the new method allows fast experimentation while providing the same information on the subsurface formation as prior-art methods.
  • FIG. 5 shows an example of an application to a formation having a double porosity.
  • the fluid produced by the formation is contained in the matrix, i.e. in the rock making up the formation, and in the interstices or cracks contained in the matrix.
  • the fluid, which moves relatively rapidly out of the cracks is replaced relatively slowly by the matrix. Owing to the more disturbed evolution which results for the experimental pressure curve in its straight part, matching takes place precisely and without ambiguity and enables a clear distinction of the homogeneous and heterogeneous behaviors.
  • the part of the method of the invention which consists in determining the characteristics of the subsurface formation from the experimental data can of course be implemented by means of a computer which would have the type curves in memory.
  • the experimental data would be furnished to the computer, which would transform them as indicated above (multiplication by t P or by ⁇ t) and would automatically determine the sought characteristics.
  • computer programs are commercially available at the present time for type curve matching.

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US06/767,216 1984-08-29 1985-08-19 Hydrocarbon well test method Expired - Fee Related US4677849A (en)

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FR8413359 1984-08-29
FR8413359A FR2569762B1 (fr) 1984-08-29 1984-08-29 Procede d'essai de puits d'hydrocarbures

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4761997A (en) * 1984-11-20 1988-08-09 Veli Reijonen Oy Ground water well dimensioning procedure
US4860581A (en) * 1988-09-23 1989-08-29 Schlumberger Technology Corporation Down hole tool for determination of formation properties
US4862962A (en) * 1987-04-02 1989-09-05 Dowell Schlumberger Incorporated Matrix treatment process for oil extraction applications
US4936139A (en) * 1988-09-23 1990-06-26 Schlumberger Technology Corporation Down hole method for determination of formation properties
GB2235540A (en) * 1989-08-31 1991-03-06 Applied Geomechanics Inc Evaluating properties of porous formation
GB2312456A (en) * 1996-04-23 1997-10-29 Elf Aquitaine Determining the nature of a production well and reservoir
US20040261505A1 (en) * 2001-08-02 2004-12-30 Eni S.P.A. Method for the determination of the wall friction profile along pipes by pressure transients measurements
US6993963B1 (en) * 2000-09-22 2006-02-07 Jon Steinar Gudmundsson Method for determining pressure profiles in wellbores, flowlines and pipelines, and use of such method
EP1883801A2 (en) * 2005-05-25 2008-02-06 Geomechanics International, Inc. Methods and devices for analyzing and controlling the propagation of waves in a borehole generated by water hammer
US20110130966A1 (en) * 2009-12-01 2011-06-02 Schlumberger Technology Corporation Method for well testing
CN101560879B (zh) * 2008-04-15 2013-06-19 中国石油大学(北京) 用于低渗透气藏的试井分析控制系统及方法
CN103899300A (zh) * 2014-03-25 2014-07-02 中国石油天然气股份有限公司 一种基于示功图的二流量试井分析的方法及系统
CN112211626A (zh) * 2020-10-30 2021-01-12 西南石油大学 一种非均质气藏气井产能试井测试类型的优选方法

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3321965A (en) * 1964-10-08 1967-05-30 Exxon Production Research Co Method for testing wells
US3550445A (en) * 1968-01-19 1970-12-29 Exxon Production Research Co Method for testing wells for the existence of permeability damage
US3636762A (en) * 1970-05-21 1972-01-25 Shell Oil Co Reservoir test
US4328705A (en) * 1980-08-11 1982-05-11 Schlumberger Technology Corporation Method of determining characteristics of a fluid producing underground formation
US4597290A (en) * 1983-04-22 1986-07-01 Schlumberger Technology Corporation Method for determining the characteristics of a fluid-producing underground formation
US4607524A (en) * 1985-04-09 1986-08-26 Scientific Software-Intercomp, Inc. Method for obtaining a dimensionless representation of well pressure data without the use of type-curves

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3321965A (en) * 1964-10-08 1967-05-30 Exxon Production Research Co Method for testing wells
US3550445A (en) * 1968-01-19 1970-12-29 Exxon Production Research Co Method for testing wells for the existence of permeability damage
US3636762A (en) * 1970-05-21 1972-01-25 Shell Oil Co Reservoir test
US4328705A (en) * 1980-08-11 1982-05-11 Schlumberger Technology Corporation Method of determining characteristics of a fluid producing underground formation
US4597290A (en) * 1983-04-22 1986-07-01 Schlumberger Technology Corporation Method for determining the characteristics of a fluid-producing underground formation
US4607524A (en) * 1985-04-09 1986-08-26 Scientific Software-Intercomp, Inc. Method for obtaining a dimensionless representation of well pressure data without the use of type-curves

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
World Oil, vol. 196, No. 6, pp. 95 106, May 1983, D. Bourdet, etc. *
World Oil, vol. 196, No. 6, pp. 95-106, May 1983, D. Bourdet, etc.

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4761997A (en) * 1984-11-20 1988-08-09 Veli Reijonen Oy Ground water well dimensioning procedure
US4862962A (en) * 1987-04-02 1989-09-05 Dowell Schlumberger Incorporated Matrix treatment process for oil extraction applications
US4860581A (en) * 1988-09-23 1989-08-29 Schlumberger Technology Corporation Down hole tool for determination of formation properties
US4936139A (en) * 1988-09-23 1990-06-26 Schlumberger Technology Corporation Down hole method for determination of formation properties
GB2235540A (en) * 1989-08-31 1991-03-06 Applied Geomechanics Inc Evaluating properties of porous formation
US5220504A (en) * 1989-08-31 1993-06-15 Applied Geomechanics Evaluating properties of porous formations
GB2312456A (en) * 1996-04-23 1997-10-29 Elf Aquitaine Determining the nature of a production well and reservoir
US5959203A (en) * 1996-04-23 1999-09-28 Elf Aquitaine Production Method for automatic identification of the nature of a hydrocarbon production well
GB2312456B (en) * 1996-04-23 1999-12-08 Elf Aquitaine Method for automatic identification of the nature of a hydrocarbon production well
US6993963B1 (en) * 2000-09-22 2006-02-07 Jon Steinar Gudmundsson Method for determining pressure profiles in wellbores, flowlines and pipelines, and use of such method
US20040261505A1 (en) * 2001-08-02 2004-12-30 Eni S.P.A. Method for the determination of the wall friction profile along pipes by pressure transients measurements
US7240537B2 (en) * 2001-08-02 2007-07-10 Eni S.P.A. Method for the determination of the wall friction profile along pipes by pressure transients measurements
EP1883801A2 (en) * 2005-05-25 2008-02-06 Geomechanics International, Inc. Methods and devices for analyzing and controlling the propagation of waves in a borehole generated by water hammer
EP1883801A4 (en) * 2005-05-25 2011-02-23 Geomechanics International Inc METHODS AND DEVICES FOR ANALYZING AND CONTROLLING WAVE PROPAGATION IN A BOREHOLE GENERATED BY A BEIER BREAK
CN101501298B (zh) * 2005-05-25 2013-09-25 地质力学国际公司 分析和控制在钻孔中水锤产生的波传播的方法和装置
CN101560879B (zh) * 2008-04-15 2013-06-19 中国石油大学(北京) 用于低渗透气藏的试井分析控制系统及方法
US20110130966A1 (en) * 2009-12-01 2011-06-02 Schlumberger Technology Corporation Method for well testing
CN103899300A (zh) * 2014-03-25 2014-07-02 中国石油天然气股份有限公司 一种基于示功图的二流量试井分析的方法及系统
CN112211626A (zh) * 2020-10-30 2021-01-12 西南石油大学 一种非均质气藏气井产能试井测试类型的优选方法
CN112211626B (zh) * 2020-10-30 2022-03-11 西南石油大学 一种非均质气藏气井产能试井测试类型的优选方法

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FR2569762A1 (fr) 1986-03-07
DE3561964D1 (en) 1988-04-28
NO164432B (no) 1990-06-25
CA1259819A (en) 1989-09-26
EP0174890B1 (fr) 1988-03-23
FR2569762B1 (fr) 1986-09-19
NO164432C (no) 1990-10-24
EP0174890A1 (fr) 1986-03-19
NO853376L (no) 1986-03-03

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